1. Field of the Invention
The present invention relates generally to flashing electrically erasable programmable read-only memories (EEPROMs). More particularly, the preferred embodiments of the present invention are directed to broadcasting images to be flashed to multiple EEPROMs, where the broadcasting occurs to each system supporting the EEPROM flashing substantially simultaneously. Also, the preferred embodiments are directed to reducing the size of the image to be flashed in the broadcast stage of the image transfer by predefining a frequency table for Huffman encoding, and using that frequency table thereafter for encoding and decoding each image transferred. In this way, the Huffman frequency table need not be transferred with the image.
2. Background of the Invention
Every computer system has memory devices with varying degrees of volatility. For example, almost every computer system has random access memory (RAM) for use by the microprocessor in temporarily storing data and programs. However, the contents of the RAM are lost when the computer system is powered down. Computers likewise have some kind of read-only memory (ROM). This ROM generally contains system boot information and basic input/output system (BIOS) programs. The contents of a standard ROM are not lost with a cycle of the power of the computer. This ROM could comprise many different types of read-only memory including ROM that may only be written one time (programmable read-only memory (PROM)), and various PROMs such as ultraviolet erasable PROMs (UVPROMs) and electrically erasable PROMs (EEPROMs). A particular kind of PROM known as flash EEPROM has found particular acceptance. The “flash” portion of the description ostensibly coming from the fact that this particular kind of EEPROM may be erased and rewritten relatively quickly, as compared to a UVPROM, which must be removed from the computing device and placed under ultraviolet light just to be erased.
Flashing EEPROM in the context of computer systems may also take place quickly because of a relatively high bandwidth communication buses between computer system components. Thus, when an EEPROM needs to be flashed, e.g., to update the BIOS, the new software image is transferred from a storage medium of the computer, e.g., a floppy drive, to the EEPROM. The time it takes to transfer the new software image over the high bandwidth bus is relatively insignificant. However, problems arise when the communication pathway between the long-term storage medium and the EEPROM is of low bandwidth. The problems arise in the amount of time it takes to transfer the image across that low bandwidth pathway.
Further, there may be multiple flash EEPROMs that need to be updated coupled to the low bandwidth bus. The amount of time to transfer the image to be flashed thus increases considerably given that the prior art method of transferring these images are to transfer them one at a time.
Thus, what is needed in the art is a way to minimize the amount of time it takes to transfer software images to remote EEPROMs across a low bandwidth bus, especially where the new image is used to flash each downstream EEPROM, and also where the new images are related to the old images on the EEPROMs.